[Model] add qwen2-audio support in vllm.entrypoints.openai.api_server

[zjjzyl]

This PR adds qwen2-audio support in vllm.entrypoints.openai.api_server.

So we can use python -m vllm.entrypoints.openai.api_server --served-model-name qwen2_audio --model model_path --host 0.0.0.0 --port xx to start a qwen2-audio service.

[github-actions]

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